278 COLEUPTERA OF NORTH AMERICA. 



and almost poiuted bebiud, aud luc cpiiinji-a are uot longer Iban 

 the epistenia. 



In the 1 the 5th ventral seguieiit is transverse, and the Cth is 

 visible; in the 9 the 5th is prolonged, and Gth not visible. 



The scutellum is always rounded behind; the mesonotum is 

 punctured at the sides, the stridulating plate is wanting in 

 Teti-opium; feebly developed, and divided by a broad median 

 vitta in Criocephalus; tolerably large aud channelled in Asenuun 

 aud Nothorhiua ; large and undivided, as in most Cerambycini, 

 in Opsimus, and Smodicum. 



An undifferentiated, or synthetic tribe, having affinities in vari- 

 ous directions ; the maxillary lobes are very feebly developed, 

 and almost atrophied in Asemura, showing an affinity with Spon- 

 dylis and Prionida? ; the divided stridulating plate indicates a 

 relation with Lepturini; Tetropium diverges towards Callidium, 

 Criocephalus with its coarsely granulated eyes tends towards the 

 genuine Cerambycini, while Opsimus and Smodicum seem to be 

 entirely isolated, having no relation with other members of our 

 fauna. 



The groups may be thus separated : — 



I'lpimera of niesothorax normal, truncatt^ at inner end ; 



Base of prothorax normal. Apemi. 



Base of j^rotliorax emarginate, filled by a thin plate. Opsimi. 



Eiiimera of mesotliorax acutely pointed internally. Smodici. 



Group I. — Asemi. 



The insects of this group are generally Callidioid in form, the 

 head short, the mandibles small, stout, and acute, the palpi nearly 

 equal, or rarely unequal (Tetropium); the eyes finely or mode- 

 rately coarsely (Criocephalus) granulated, transverse, scarcely 

 emarginate (Asemum), large, more or less emarginate (Crioce- 

 phiilns), divided (Tetropium). 



All the genera except Cyamophthalnuis, which has the last joint 

 of the palpi subulate, are represented in our fauna, and are dis- 

 tributed on both sides of the continent. 



Eyes mod(^rati', transverse, finely granulated, hairy ; 



Antenna? finely pubescent. Asemum. 



Antennse coarsely pubescent. Nothorhina. 



Eyes large, coarsely granulated, not linirv. Criocephalus. 



Eyes divided, rather finely granulated. Tetropium 



